Influenza virus infection is considered a major worldwide public health problem. Seasonal infections with the most common influenza virus strains (e.g. H1N1) can usually be resolved, but they still cause a high rate of mortality. The factors that influence the outcome of the infection remain unclear. Here we show that deficiency of IL-6 or IL-6 receptor is sufficient for normally sublethal doses of H1N1 influenza A virus to cause death in mice. IL-6 is necessary for the resolution of influenza infection by protecting neutrophils from virus-induced death in the lung and by promoting neutrophil-mediated viral clearance. Loss of IL-6 results in persistence of influenza virus in the lung leading to pronounced lung damage and, ultimately, death. Thus, we demonstrate that IL-6 is a vital innate immune cytokine in providing protection against influenza A infection. Genetic or environmental factors that impair IL-6 production or signalling could increase mortality to influenza virus infection.

Of the three critical enhancer elements that mediate ␤-cell-specific and glucose-responsive expression of the insulin gene, only the identity of the transcription factor binding to the RIPE3b element (RIPE3b1) has remained elusive. Using a biochemical purification approach, we have identified the RIPE3b1 factor as a mammalian homologue of avian MafA/L-Maf (mMafA). The avian MafA is a cell-type determination factor that expressed ectopically can trigger lens differentiation program, but no mammalian homologue of avian MafA has previously been identified. Here, we report cloning of the human mafA (hMafA) and demonstrate that it can specifically bind the insulin enhancer element RIPE3b and activate insulingene expression. In addition, mMafA has a very restrictive cellular distribution and is selectively expressed in pancreatic ␤ but not in ␣ cells. We suggest that mMafA has an essential role in the function and differentiation of ␤-cells and thus may be associated with the pathophysiological origins of diabetes. Pancreatic ␤-cells synthesize and secrete insulin, which is essential for the maintenance of normal metabolism. Thus, a reduction in the functional mass of pancreatic ␤-cells results in diabetes. ␤-cell-specific expression of the insulin gene is regulated by transcription factors binding to three conserved insulin enhancer elements [E1 (Ϫ100 to Ϫ91 bp), A3 (Ϫ201 to Ϫ196 bp) and RIPE3b (Ϫ126 to Ϫ101 bp)] (1-5). Two of the three factors binding to these elements, PDX-1 and BETA2, have been identified and found to have profound roles in regulating pancreatic development and the differentiation of ␤-cells (6-13). Thus, transcription factors regulating insulin gene expression are key mediators of development, differentiation, and function of ␤-cells. Hence, identification and characterization of insulin gene transcription factors is critical for understanding the pathophysiology of diabetes.Pancreatic ␤-cell-specific insulin gene expression results from the expression of a unique combination of PDX-1, BETA2, and RIPE3b1 factors in this cell type. The transcription factor PDX-1 is expressed in pancreatic ␤-cells and has a heterogeneous expression pattern in other pancreatic cell types and in the duodenum (6)(7)(8)(9)(10)14). BETA2 is expressed in all pancreatic endocrine cell types, some intestinal endocrine cells, and the brain (11-13). The cellular distribution of RIPE3b-binding activity has been characterized by electrophoretic mobility-shift assay (EMSA) with nuclear extracts from both insulin-producing and non-insulin-producing cell lines (2,3,15,16). Two specific RIPE3b-binding complexes have been identified:(i) RIPE3b1 detected only in pancreatic ␤-cell lines, and (ii) the RIPE3b2-binding complex detected in all cell lines examined. The binding of these transcription factors to the A3, E1, and RIPE3b elements also regulates glucose-mediated alterations in insulin gene expression (3,(17)(18)(19). Our earlier studies demonstrated that the binding activity of the RIPE3b1 activator was induced in response to a...

Nur77, an orphan nuclear receptor, plays a key role in apoptosis in T cells. In cancer cell lines, Nur77 can induce apoptosis through the intrinsic apoptotic pathway, but the mechanism by which Nur77 kills T cells remains controversial. In this study, we provide biochemical, pharmacological, and genetic evidence demonstrating that Nur77 induces apoptosis through the activation of the intrinsic pathway in T cells. We also show that Nur77 is a physiological substrate of the MEK-ERK-RSK cascade. Specifically, we demonstrate that RSK phosphorylates Nur77 at serine 354 and this modulates Nur77 nuclear export and intracellular translocation during T cell death. Our data reveal that Nur77 phosphorylation and mitochondrial targeting, regulated by RSK, defines a role for the MEK1/2-ERK1/2 cascade in T cell apoptosis.

Upon stimulation by the transforming growth factor ␤ (TGF-␤), Smad2 and Smad3 are phosphorylated at their C termini and assemble into stable heteromeric complexes with Smad4. These complexes are the functional entities that translocate into the nucleus and regulate the expression of TGF-␤ target genes. Here we report that the TGF-␤-activated phospho-Smad3/Smad4 complex utilizes an importin-independent mechanism for nuclear import and engages different nucleoporins for nuclear import compared with the monomeric Smad4. Within the heteromeric complex, phospho-Smad3 appears to dominate over Smad4 in the nuclear import process and guides the complex to its nuclear destination. We also demonstrate that the binding of phosphoSmad3 to Smad4 prevents Smad4 from interacting with the nuclear export receptor chromosome region maintenance 1. In this way, TGF-␤ signaling suppresses nuclear export of Smad4 by chromosome region maintenance 1 and thereby targets Smad4 into the nucleus. Indeed tumorigenic mutations in Smad4 that affect its interaction with Smad2 or Smad3 impair nuclear accumulation of Smad4 in response to TGF-␤.

SARS-CoV-2 infection results in a spectrum of outcomes from no symptoms to widely varying degrees of illness to death. A better understanding of the immune response to SARS-CoV-2 infection and subsequent, often excessive, inflammation may inform treatment decisions and reveal opportunities for therapy. We studied immune cell subpopulations and their associations with clinical parameters in a cohort of 26 patients with COVID-19. Following informed consent, we collected blood samples from hospitalized patients with COVID-19 within 72 h of admission. Flow cytometry was used to analyze white blood cell subpopulations. Plasma levels of cytokines and chemokines were measured using ELISA. Neutrophils undergoing neutrophil extracellular traps (NET) formation were evaluated in blood smears. We examined the immunophenotype of patients with COVID-19 in comparison to that of SARS-CoV-2 negative controls. A novel subset of pro-inflammatory neutrophils expressing a high level of dual endothelin-1 and VEGF signal peptide-activated receptor (DEspR) at the cell surface was found to be associated with elevated circulating CCL23, increased NETosis, and critical-severity COVID-19 illness. The potential to target this subpopulation of neutrophils to reduce secondary tissue damage caused by SARS-CoV-2 infection warrants further investigation.

We evaluated the number of CD26 expressing cells in peripheral blood of patients with COVID‐19 within 72 h of admission and on day 4 and day 7 after enrollment. The majority of CD26 expressing cells were presented by CD3 + CD4 + lymphocytes. A low number of CD26 expressing cells were found to be associated with critical‐severity COVID‐19 disease. Conversely, increasing numbers of CD26 expressing T cells over the first week of standard treatment was associated with good outcomes. Clinically, the number of circulating CD26 cells might be a marker of recovery or the therapeutic efficacy of anti‐COVID‐19 treatment. New therapies aimed at preserving and increasing the level of CD26 expressing T cells may prove useful in the treatment of COVID‐19 disease.

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Objective SARS-CoV-2 infection has been shown to result in increased circulating levels of adenosine triphosphate and adenosine diphosphate and decreased levels of adenosine, which has important anti-inflammatory activity. The goal of this pilot project was to assess the levels of soluble CD73 and soluble Adenosine Deaminase (ADA) in hospitalized patients with COVID-19 and determine if levels of these molecules are associated with disease severity. Methods Plasma from 28 PCR-confirmed hospitalized COVID-19 patients who had varied disease severity based on WHO classification (6 mild/moderate, 10 severe, 12 critical) had concentrations of both soluble CD73 and ADA determined by ELISA. These concentrations were compared to healthy control plasma that is commercially available and was biobanked prior to the start of the pandemic. Additionally, outcomes such as WHO ordinal scale for disease severity, ICU admission, needed for invasive ventilation, hospital length of stay, and development of thrombosis during admission were used as markers of disease severity. Results Our results show that both CD73 and ADA are decreased during SARS-CoV-2 infection. The level of circulating CD73 is directly correlated to the severity of the disease defined by the need for ICU admission, invasive ventilation, and hospital length of stay. Low level of CD73 is also associated with clinical thrombosis, a severe complication of SARS-CoV-2 infection. Conclusion Our study indicates that adenosine metabolism is down-regulated in patients with COVID-19 and associated with severe infection. Further large-scale studies are warranted to investigate the role of the adenosinergic anti-inflammatory CD73/ADA axis in protection against COVID-19.